University of Queensland

Kasper Johansen

Summary | Research Objectives | Supervisors |

Summary

Riparian zones are vital elements of the savanna landscape (Tropical Savannas CRC, 2002), but human-induced degradation of these environments has in many areas been considerable (Begg et al. , 2001; Cowie & Werner, 1993; LWRRDC, 1999a). Other than ground-based vegetation, faunal and stream surveys, there is a significant lack of monitoring techniques able to provide regularly updated and spatially extensive information on recognized indicators of riparian environment condition from local to regional scales (1–1000km²).

The research project will concentrate on developing a framework for cost-effective monitoring of riparian zones in Australian tropical savannas at local to regional scales using field and remote sensing data.

The landscapes of dense grass and scattered trees that stretch across northern Australia are characterised ecologically as tropical savannas. Sustainable use and management of resources in these areas are critical factors that affect the ecology and environment (Begg et al. , 2001; NTG, 2003; Tropical Savannas CRC, 2002).

Riparian zones are defined as the interface of terrestrial and aquatic ecosystems and they encompass sharp gradients of environmental factors, ecological processes, and plant communities. Boundaries of riparian zones extend outwards to the limits of flooding and upward into the canopy of streamside vegetation (Gregory et al. , 1991). Riparian vegetation provides a number of important functions including:

• nutrients to streams from litter fall;
• root masses for stream bank stability;
• shade to control water temperature and algal growth;
• large woody debris for stream channel development; and
• natural filtering preventing pollutants from entering the waterways (Congalton et al. , 2002; Dowe, 2003; LWRRDC, 1999a; LWRRDC, 1999b).

The contribution of savanna riparian zones to biodiversity, cultural values and the economy is disproportionate to the small area they occupy (Tropical Savannas CRC, 2002). It is important to maintain savanna and in-stream biodiversity, stream channel morphology and water quality. However, savanna riparian zones are highly vulnerable to the effects of disturbances such as weed invasion, feral animals, fire impact, overgrazing and altered flow regimes (Begg et al. , 2001; Finlayson & von Oertzen, 1996). Threats to riparian health are compounded by the fact that riparian zones are the focus of much activity related to the development of northern Australia such as grazing, agriculture, weed invasion, tourism, and water extraction for agricultural and domestic purposes. The concentration of land use in these habitats is likely to increase in the future, thus increasing the need for practical management options in riparian zones that will allow landholders to meet their management objectives while still maintaining riparian health (Apan et al. , 2002; Begg et al. , 2001; Bourgeau-Chavez et al. , 2001; NTG, 2003; Tropical Savannas CRC, 2002).

Developing practical management options for riparian zones requires:

• a definition of riparian health;
• practical methods for assessing riparian health;
• an understanding of the effects of potentially threatening processes on riparian health; and
• an evaluation of techniques to manage those threats (Tropical Savannas CRC, 2002).

This research project will address all of these issues and base the methodology on both field surveying and remote sensing.

Research Objectives

Primary Objective

• To establish a framework for cost-effective monitoring of riparian zones in Australian tropical savannas over local to regional scales using field and remote sensing data.

Secondary Objectives

• To identify how environmental features (grass cover, canopy structure, leaf angles, soils, water, exposed sandy surfaces, etc.) and variables (phenology, water availability, weeds, fires, etc.) within savanna riparian zones affect remotely sensed image data spatially, spectrally, radiometrically and temporally.
• To map savanna riparian areas using field and multiple spatial resolution image data collected for the Daly River and South Alligator River / Barramundie Creek areas in the Northern Territory. Field data will be integrated with the image data to map riparian health indicators. Furthermore, field data will be used for training and validation purposes of the multiple spatial resolution image data.
• To monitor savanna riparian areas over time using field and multiple spatial resolution image data collected for the Daly River and South Alligator River in the Northern Territory. Issues related to the use of the same and different sensors for change detection analyses of savanna riparian areas (location and width of wavebands, radiometry, spectral response functions, topography, atmospheric condition, solar angle, viewing angle, geometric coregistration, phenology, climatic factors, etc.) will be addressed.
• To develop and validate the framework for monitoring savanna riparian areas using field and multiple spatial resolution image data.

Supervisors

Dr Stuart Phinn, University of Queensland
Robert Karfs, NTDPIE